This isn’t the first time I’ve ranted about bad mulch choices and it certainly won’t be the last. But this pictorial cautionary tale is too important to pass up.
We already know that sheet mulches can be death to microbes, plant roots and animals living in the soil underneath. Our newly published research shows that landscape fabric reduces carbon dioxide movement between the soil and atmosphere about 1,000 times more than wood chip mulches do: plastic mulches are even worse. Oxygen movement will be likewise affected. And while gaps and holes in these barriers can lessen the impact, the question remains: why would you use ANY mulch that reduces gas movement? Yet people persist in using fabrics and plastics, usually to “smother” weeds (and that verb should set off alarm bells for anyone thinking about collateral damage to soil life). But weeds are weeds for a reason, and they will eventually colonize the surface of sheet mulches as soil, organic matter, and water collect over time.
So without further ado, here is a case study of what happens when sheet mulch is used for landscape weed control.
These irrigated landscape beds are in Wenatchee, Washington, which has hot, dry summers. As you can see, bark mulch has been used to hide the shame of sheet mulching. And from a distance it looks…okay.
Upon closer inspection, you can see the shroud of death emerging from the bark mulch (which has no means of staying in place, especially on a slope).
And even close you can see the soil that’s blown in, along with the bark and other organic matter. Just add water, and you get weeds!
Weeds, weeds, weeds! Lots of weeds. Sunny weeds!
And shady weeds!
The weeds are thriving – but the trees are not. The crowns are dying…
…and the trunks are suckering.
But you’ll note that the trees in the first photo outside of the beds are thriving.
And it’s all because of that “weed control fabric.” Which is working so well that this landscape had to be treated with herbicide the day I was there – to control the weeds.
One of the “advantages” of being in the same office suite as me is hearing (a) that arborist wood chips are about as close to a miracle product as you can get and (b) that landscape fabric is hell on (the) earth. So my office mate Liz, either because she was convinced of the above or just wanted to shut me up, decided to rip out the landscape fabric in her ornamental bed and replace it with wood chips. She even made it a family project, somehow convincing her two young daughters that this was “fun.” Here’s her pictorial essay of the process.
Before the switch
Why on earth does anyone still believe that “weed block” fabric actually does anything remotely related to controlling weeds? It provides a great substrate for all those weed seeds blowing around, which find themselves the recipients of any rainfall or irrigation. They germinate and grow like crazy – because they are WEEDS. It’s what they do.
Worse yet for the soil – all of those pores in the fabric that supposedly allow water and oxygen to move through are soon filled with bits of soil. The resulting mat is anything but permeable. But weeds love it!
First Liz had to score some woodchips, which as you can see pretty much filled her driveway. The girls, however, thought they were a great addition.
Next, all of that fabric had to come out. This is not an easy process, because the surface of the fabric was completely colonized by weeds. A mattock is a great tool for getting this done.
Now, let’s look at the soil underneath the fabric. You can see how dry it is. That’s because even during our rainy springs in the Pacific Northwest all of the rainfall stays on top of the fabric, allowing lush weed growth. The roots of all of the landscape plants get virtually none of this, and in the summer that’s a source of chronic drought stress.
Fortunately, the soil underneath, while dry, looks pretty good. Once the shrubs and perennials are able to take advantage of the increased water and oxygen they will thrive.
Maybe you don’t like the look of arborist wood chips, but it’s certainly better than the weedy mess that used to be there. Plus, the soil benefits from the increased water and oxygen, the beneficial microbes in the wood chips, and the slow feed of nutrients as those chips slowly decompose.
If you are ready to switch from “fabric fail” to “wood-chip win,” you can start with this fact sheet which will guide you through the process.
In my educational seminars I’ve long shared a version of the CRAAP test (currency, relevance, authority, accuracy, and purpose) for analyzing information related to gardens and landscapes. My version is CRAP (credibility, relevance, accuracy, purpose), and we’ve published an Extension Manual that explains in detail how to apply it. This past week I was at the Philadelphia Flower Show participating in Bartlett’s Tree Care Update panel. Given that the theme of the show was “Flower Power,” I figured that a talk on Magical Mystery Cures was in order. And the 1960’s was the decade where the late Jerry Baker gained prominence as a garden authority – and whose presence is still widely felt nearly 60 years later.
Now, I could spend the rest of the year discussing all of Jerry’s advice, tips, and tonics for gardens – but it’s more useful to determine whether he is a credible source of reliable information. So let’s apply the CRAP test.
C = credibility. What are Jerry’s credentials as a garden expert? It’s easy to find this information from the internet, including the Jerry Baker website. He had no academic training in plant or soil sciences but started his career as an undercover cop who often posed as a landscaper. His books are all popular publications, meaning they have not gone through critical review by experts before publication.
R = relevance. For our purposes, his information is relevant to our focus of managing gardens and landscapes (as opposed to production agriculture, for instance).
A = accuracy. Jerry’s advice is not based on any scientific source. He relies on common-sense approaches, folklore, and his grandmother’s advice. In fact, many of his assertions are at odds with published scientific evidence. Now, science evolves, and older scientific publications are sometimes found to be inaccurate after new information comes to light. If Jerry’s books were meant to be accurate sources of information, they would be updated with new findings as subsequent editions were published. This is what happens with textbooks, for example.
P = purpose. What is Jerry’s ultimate purpose? It’s sales. There’s no way around this conclusion. Over twenty million copies of his books have been sold, and during his career he became the spokesperson for several gardening products. Probably the most well-known of these was the Garden Weasel (which parenthetically is a great way to destroy fine roots and soil structure). There’s no doubt he was a brilliant self-promoter and marketer. But he was not a reliable resource, and many of his “tips and tonics” are extraordinarily harmful to plants, pets, and the environment.
While I was wrapping up my research on Jerry Baker I was particularly taken by a chapter in one of his books (one of his Back to Nature Almanacs) called “The Tree Quacks.” I thought some of these quotes were particularly ironic:
Imagine my surprise when I discovered that these quotes were actually not his own. In fact, the entire chapter was plagiarized from a 1964 article by John Haller in Popular Science, which is online. This action is uncomfortably similar to his 1985 trademarking of the phrase “America’s Master Gardener,” 12 years after the Master Gardener program was formed (but not trademarked) at Washington State University.
I hope this post has helped you learn to analyze the credibility of information and information sources. If so, you can claim the of America’s Master CRAPper ™!
As many of you know, the Garden Professors host a Facebook group dedicated to the discussion of science-based practices for gardens and landscapes. (Side note – if you haven’t joined us please do!) Recently we’ve had a spate of “what’s wrong with my plant” posts, usually focusing on some leaf issue and little other information. And far too often an eager group member will jump in with a fertilizer recommendation. So today’s blog post has two objectives: explaining why you can’t reliably diagnose problems from a picture of suffering leaves and why blanket fertilizer recommendations should be avoided.
To illustrate the problem with armchair diagnosis, consider this photo below.
Now there are two ways to ask a question here: the first is “what’s wrong with these leaves” and the second is “what’s wrong with my plant.” We can easily answer the first one: there is nutrient deficiency in the leaves, most probably iron or manganese. But that does NOT mean there is a deficiency in the soil. So we can’t address “what’s wrong with my plant” because we don’t have enough information.
How can we determine what’s wrong? My first question to the poster is invariably “have you had a soil test?” Soil test results will indicate whether the element in question is actually deficient, and will provide levels of other nutrients that could interfere with root uptake. If there’s no deficiency of the nutrient in question, then adding fertilizer is not going to help! And adding fertilizer unnecessarily can create further soil nutrient imbalances and contribute to environmental pollution.
Once we have the soil test results, we can then begin to address “what’s wrong with my plant.” But not from the original picture. (If you are curious about what else could be causing this problem, check out this blog post from 2011.)
Let’s try another. Consider the leaves in this photo:
We now know to ask “what’s wrong with these leaves?” Ignore for now the deficiencies in the older leaves and look at the size of youngest ones compared to the older. The answer is fairly straightforward here: there was too little water available when the newly emerging leaves were expanding. Leaf expansion depends on turgor pressure – the higher the turgor pressure, the larger the leaves get. Once expansion stops, protective plant biochemicals are laid down which prevent further expansion. By comparing the youngest leaves to the leaves from previous years, you can see that they are significantly smaller. But why?
Again, we need more information before we can answer “what’s wrong with my plant.” Was there too little available soil water during leaf expansion? It’s possible, but this example is from western Washington State, a climatic region with wet springs. Most likely there is an issue with the roots. My first question with these cases is “can you easily move the plant in the ground?” This is my “wiggle test” – a way to determine if roots are established. In this case – and in nearly every case like this that I’ve seen personally – the roots are NOT established. Often this is because the plant (1) was not bare-rooted at planting and/or (2) was planted too deeply. Without decent root establishment there is not enough water uptake to support full turgor in expanding leaves.
Lack of an established root system also account for the interveinal chlorosis you can see in the oldest leaves. These leaves are fully expanded, probably because the plant was still at the nursery when these leaves emerged. But their color is off. A root system that doesn’t supply sufficient water for leaf expansion is by default not going to provide sufficient nutrients, either. Adding fertilizer to this plant is not going to help! It needs to be dug up and replanted correctly or replaced. It is never going to thrive under the current conditions.
Armchair diagnosis can be accurate and fun if you follow a set of guidelines to extract more information. But simply recommending a fertilizer based on leaf appearance is neither science-based nor environmentally responsible.
By Jeff Gillman (posted by Linda C-S, who has taken liberties with using photos from UNC Charlotte gardens that have nothing to do with Jeff’s post.)
It has been almost two years since I have had the chance to post anything as a Garden Professor. Since then I’ve taken a job as the Director of UNC Charlotte Botanical Gardens and there are all kinds of things I’d like to share with you, and perhaps sometime over the next few weeks and months I will, but for now what is probably most pertinent is that I absolutely love my job. I am still doing some work on garden myths, but what I’m finding more entertaining is investigating the histories of different plants and their interactions with humans. In fact, in about a month or so, my friend Cindy Proctor and I will be releasing a podcast titled The Plants We Eat that investigates the interesting history, culture and biology of the various plants we use for food. We’ve already recorded shows on strawberries, grapes and mad honey, and we’ll be doing shows on apples, figs, and a few others before we release it – we want to have a decent backlog of shows so that we can maintain a pace of one podcast a week.
But enough about me! The current Gardens Professors called my attention to a recent article titled “The effect of ad hominem attacks on the evaluation of claims promoted by scientists”, and I found it informative to say the least. This article provides instructions on how to stop people from trusting a particular study.
No, seriously. If you wanted to you could actually rewrite this as a short manual on how to make people question the results of any scientific study.
And if you did I think it would look kind of like this:
(Short Disclaimer – I’m pretty sure that the authors of the above article never intended it to be taken in the way I’m presenting it. I’m posting this purely as satire.)
So, someone has published a scientific article that you disagree with. Hey, we’ve all been there. Scientific evidence that contradicts your beliefs/works/preconceived notions sucks, but it isn’t the end of the world. There are things you can do.
You might consider conducting your own well-designed experiments that would call into question some of the claims of the offending work. Once upon a time this was been the standard way to address this kind of problem, but this could take months or even years to accomplish. And the truth of the matter is that your experiment might not even say what you want it to and even if it does, with attention spans the way they are, nobody will even remember what you’re even talking about when your paper comes out.
Which is to say, there are better, faster ways to take care of inconvenient research, and that’s where this convenient manual comes into play.
First, realize that attacking the research itself isn’t a sure thing. Sure, it’s the right thing to do, but morals be damned, attacking the research itself can be waaaayyy too technical. People won’t understand what you’re talking about, so forget about it.
Attacking researchers personally by making nasty comments about where they graduated from college or that they do sloppy research would seem like winner, that kind of attack just doesn’t cut it today. Maybe it’s the political climate, but, to their credit, people just aren’t responding to non-specific personal attacks the way they once did.
So you’ve got to be smart and hit them where it hurts. You could say that data was fabricated in the paper that you want to discredit, but this could be problematic if it isn’t true. Not to worry. All you really need to do is find an instance where the researcher did do something wrong. In fact, it’s possible that some past misconduct could be even more effective at discrediting a paper than misconduct on the paper in question itself.
The gold standard, however, is conflict of interest. By establishing that the researcher who has caused you grief has some sort of conflict of interest you can cause people to question the results of research just about as effectively as if some sort of misconduct had taken place, and conflicts of interest are much easier to find! You could blame a company, a person, or even a University. Shoot, want to show that a study, which demonstrates that an herbicide is effective at controlling a weed, isn’t true? All you need to do is show that the company which makes the herbicide gave a few hundred dollars to an athletic program at the school, or show that one of the student workers in the lab has a second cousin employed by the company. It’s all good.
And so there you have it. The fast, easy way to discredit someone. And remember, just implying things can be as effective as having facts. No need to lie! Good Luck, and remember The Truth is What You Make It!
Here at the Garden Professors we try to focus on sharing the best applied plant and soil science information for gardens and landscapes. But sometimes we get sidetracked by information that is SO bad that we need to share it too. So the purpose of this occasional feature – Worst Gardening Advice – is not to poke fun, but to point out the real hazards to plants, people, and the environment by following scientifically unsound practices.
Without identifying which of my GP colleagues nominated this video, we now present how NOT to fix storm damaged trees.
I made this little image to try and make a point, not about Bt or GMOs or organic agriculture (all important topics for another day), but about the use of buzz words. I’m tired of the way words like “chemical” and “natural” get thrown around to try and make things sound bad or good. Neither of them are particularly useful terms because the definition of chemical is so broad as to cover just about anything, and “Natural” is more-or-less meaningless and entirely subjective.
So, my simple plea is to not let emotionally loaded buzz words sway you, but dig into the actual research and evidence to make decisions about what you think is good or bad.
You know the word “rogue” as a noun and adjective, and probably from when Sarah Palin “went rogue” during her time as vice presidental candidate.
But you may not know that it also a verb. That’s the way I use it most often. I rogue plants and I complain — often — about seed producers not doing enough roguing.
To rogue means to weed out inferior or off-type plants. It is a critical part of producing and maintaining seed selections of plants. Whenever you are growing fields of plants for seed production, be it tomatoes or zinnias or corn, you get off types. Chance mutations, seedlings produced from errant grains of pollen from another variety, or just change of the diversity within the population. So one has to rogue — walk through the fields and pull out flowers that are the wrong color, corn plants that aren’t yielding enough, all the unexpected variants to keep the variety true to type.
The annoying thing is that a lot of seed producers cut corners — particularly, it seems, for annual flower seed — and don’t bother. The results can be very frustrating.
The worst are flowers in mixed colors. Maintaining a good mix of multiple colors requires careful roguing to ensure one color — due to greater vigor or just chance — doesn’t come to dominate. Lots of companies just don’t seem to bother.
Last year I bought a packet of Zinnia ‘State Fair’, an old, and wonderful seed strain, which was supposed to come in the full mix of zinnia flower colors.
I got pink. That’s all. Just pink. My whole row was pink. Not my favorite color of zinnia. Clearly the pink plants slowly came to dominate the fields of whoever is producing these seeds, and instead of roguing out some to bring the color mix back into balance, they just let them go rogue, and I got stuck with just one color.
The ‘State Fair’ zinnias were also supposed to be double, like this.
They weren’t. Single flowered forms will almost always come to dominate seed strains unless rogued out because they’re easier for insects to pollinate and thus tend to produce more seed. Clearly no one bothered, because every plant I sowed out gave me just a single row of showy petals.
I’ve had similar experiences with countless other varieties of seed annuals. The picture looks great on the packet, but sow them out and mostly what I get are rogues, not the variety I was after. The lack of roguing is a plague… bad enough that a friend in the horticulture industry once mentioned casually to me that, of course, cosmos varieties are only worth growing when they are first introduced. A few years without good roguing, and their desirable characteristics are mostly lost.
So more roguing please. I love growing big blowsy annual flowers from seed. I’m tired of them all going rogue.
The end of August brought an unseasonable rain- and windstorm to the Puget Sound region. We had some spectacular tree failures which I missed seeing as I was out of town. But one of our Facebook group members, Grace Hensley, was on the ball and took some great photos of a fallen purple-leafed plum. The first thing you see is the complete lack of a stabilizing root system.
Now look at the base of the trunk, which is actually a massive circling root that has girdled the trunk over time.
By now you must be able to see the orange twine extending from the base of the tree to the soil. Yes, those are the remains of the balled-and-burlapped clay root ball that was planted many years ago. Commercial landscapers will assure you that tree roots can grow through the burlap and establish. And this is sometimes true, as in this case.
But what doesn’t happen when the whole B&B mass is plopped into the ground is that circling woody roots aren’t discovered and corrected. Over the decades what started as a small circling root grew bigger and bigger, slowly squeezing the trunk and preventing it from developing girth at that point. It’s kind of like a blood pressure cuff being pressurized but never released.
In time, the constricted point becomes so unstable that the tree breaks. Look are how small the trunk that’s still in the ground is compared to the trunk of the tree itself. Windstorms are often the final push these failing trees need.
Commercial landscapers say it’s too costly to remove the twine and burlap and clay surrounding the roots, not to mention doing any of the corrective root pruning that might be needed. It’s easier to just plant the whole thing and cross your fingers that the tree lives past the warranty date. This is what happens when you consider a tree as just another design element rather than a living organism.
As a homeowner, however, you can insist that your trees are planted correctly (if you have someone else do the work). Or you can do it yourself. The bare-root method (sometimes called root washing) is an emerging science and it requires thoughtfulness, but it’s certainly better than the conventional approach in terms of long term tree health.
I spent last week in Orlando at the ISA annual meeting (that’s the International Society for Arboriculture). It’s a great venue for networking with colleagues and hearing about the latest tree research. And once in a while I’ll have a WTF moment. (That stands for Why Trees Fail in case you’re wondering.)
My WTF experience this year revolved around some new terminology and techniques. I learned there are now “environmental arborists” who practice “retrenchment pruning.” In the last few days I’ve tried mightily to find some standard definitions from reputable sources. I don’t know what an environmental arborist is, since it’s not a certification (like an ISA certified arborist) nor is it a university degree program (like urban forestry or environmental horticulture). It seems to be a self-anointed title.
But the real WTF issue is retrenchment pruning. I looked in vain for published research through my usual data bases and found nothing – other than two articles in Arboricultural Journal (which is not the same as ISA’s journal – Arboriculture and Urban Forestry). Neither of the articles presented experimental evidence to justify this radical approach to pruning trees. Instead, they are more philosophical in nature, with a smattering of ecological theory.
Fortunately, retrenchment pruning methods are easily found on the internet, along with horrific pictures illustrating the results. As described on various websites, retrenchment pruning imitates the natural process of aging. Practitioners remove live branches or partial trunks to reduce the size of the tree and prevent future failure. These aren’t clean cuts, either: they’re “coronet cuts” or “natural fractures.” The rationale described in one of the Arboricultural Journal articles is that these jagged broken branches and trunks “promote specialist habitats and enhance colonisation rates of niche species.” In other words, this technique creates large wounds that are easily colonized by various insects and microbes.
So apparently we’re expected to ignore the well-established field of woody plant physiology (which happens to be my specialty) and related practical bodies of knowledge (e.g., formal and informal pruning techniques of said woody plants) and start hacking away at mature trees. In doing so, we’re removing live tissue and creating large wounds. This has the effect of both reducing photosynthetic potential of the tree as well as opening it up to possible pest or disease invasion. But nowhere are these possibilities discussed as part of the “natural aging process.” Nor was there mention about how to manage the epicormics shoots that result from improper pruning. And they do need to be managed.
I saw some very angry arborists at the ISA meeting who were incensed at the idea that we should deliberately malprune trees. But others seemed quite excited with this new philosophy. To paraphrase one of my plant physiology colleagues, “Give a bad arboricultural practice a catchy name and it magically becomes legitimate.”